(a) Field of the Invention
The present invention relates to an airbag cushion and an airbag system including the same, and particularly to an airbag cushion having a superior working stability and unfolding performance owing to the optimized property of seam part, a method of preparing the same, a sewing machine which can be used for such method, and an airbag system including the same.
(b) Description of the Related Art
Generally, airbag is an apparatus for protecting a driver and passengers by providing a gas into the airbag by exploding gunpowder so as to inflate the airbag after detecting crash impact with an impact detecting sensor, when a driving car collides head-on at the speed of about 40 km/h or more, and a structure of a conventional airbag system is depicted in FIG. 1.
As depicted in FIG. 1, a conventional airbag system includes an inflator 121 that generates a gas by ignition of a detonator 122; an airbag module 100 installed in a steering wheel 101 and including an airbag 124 that is expanded and unfolded toward a driver on driver's seat by the generated gas; an impact sensor 130 that gives an impact signal when the car is crashed; and an Electronic Control Module (ECM) 110 that ignites the detonator 122 of the inflator 121 according to the impact signal. In the airbag system, the impact sensor 130 detects the impact and gives the signal to the ECM, when the car collides head-on. At this time, the ECM 110 that received the signal ignites the detonator 122 and a gas generator in the inflator 121 is combusted. The combusted gas generator generates the gas rapidly and expands the airbag 124. The expanded airbag 124 contacts the front upper body of the driver and absorbs the impact load caused by the collision partially, and when the driver's head and chest go forward according to the law of inertia and smash against the airbag 124, it further absorbs the shock toward the driver by rapidly discharging the gas from the airbag through discharging holes formed on the airbag. Therefore, the airbag absorbs the shock effectively that is delivered to the driver, and can reduce the secondary injury at the time of a head-on collision.
As disclosed above, the airbag for car is prepared into a certain shape and installed in a steering wheel, side glass windows, or side pillars of the car in a folded form so as to minimize the volume, and it is expanded and unfolded when the inflator 121 operates.
At this time, a sewed airbag generally includes fabric, and seam parts for connecting the fabric. Namely, since the parts discharging air when the airbag is unfolded are the seam parts, the properties such as seam strength and elongation of the seam parts are important. Particularly, the connection performance of whole parts of the airbag must be maintained effectively so that superior expansion performance and unfolding performance are exhibited when the airbag is unfolded by instant gas generation.
However, the sewed airbag made by a common automatic sewing machine is short of the seam strength and elongation of the seam parts for providing effective expansion performance and unfolding performance when the airbag operates. The problem cannot be sufficiently overcome by changing the seam thread material applied to the seam parts, and thus the development of technology which can optimize the properties of seam parts without changing the material is required.
Therefore, the investigation for developing the airbag cushion including seam parts having superior mechanical properties and air-seal effect so as to exhibit excellent expansion and unfolding performance when the airbag is unfolded.